Porting on shotgun barrels is best described as 'unfortunate'.
Rifle 'muzzle brakes' are very effective because the mass of the powder gas is such a high percentage of the total ejecta.
With shotguns, not so much. A rifle can have 1/3 of the ejecta as gas, a shotgun perhaps 7%. Essentially an inconsequential amount, and only a portion can be redirected.
At the point of pressure relief, there is about 500 psi and the shot is accelerating at about 20 fps per inch.
Reduced recoil, yes. But not much and due mostly to less velocity. The gas redirection effect is minimal.
Better patterns? Highly debatable but possible due to less deformation in the choke, again because of reduced velocity.
Browning could sell unported guns just fine. Many people have realized just how pointless porting really is with shotguns. It mostly just makes the gun louder.
You won't see any difference game shooting, but you will likely hear it.
